1. Field of Invention
This invention pertains to method and apparatus for supplying oxygen to bodies of water used in aquaculture, and particularly to an automatic system for determining the need for oxygen and controlling the operation of aeration equipment employed therefor.
2. Prior Art and Other Considerations
The aquaculture industry has grown substantially in the last twenty-five years. Since the mid-1960s, the catfish farming industry has grown from a start-up industry to one that has produced over 400 million pounds of fish during 1991. Shrimp farming has also seen a very rapid growth curve, as well as other species of marine animals.
With the growing technology associated with the aquaculture industry, increased poundage is being produced from a given quantity of water. As a result, increased emphasis is placed on the quality of the water. One of the most critical components of water quality is oxygen content.
During daylight hours oxygen is produced in the water by photosynthesis. Oxygen depletion generally occurs during the night or early morning hours. Accordingly, in the catfish industry most of the monitoring for oxygen depletion is conducted by night crews armed with oxygen meters. In this regard, the oxygen level of a catfish pond is monitored periodically and the oxygen reading recorded. As the need for additional oxygen becomes apparent, aeration equipment is manually activated by the personnel of the night crew. Often, once supplemental aeration is begun, the tendency is to continue running it as a precaution long after the need is satisfied. This adds to the cost of aeration.
Several automated prior art devices or meters for monitoring oxygen in ponds have been developed based on an oxygen reading probe tied electronically to systems that turn on aeration equipment and send alarms. These type systems are rather temperamental and require repeated checking and calibration. These systems can be contaminated or otherwise affected by growths in the ponds. In addition, these systems are relatively expensive.
Another serious drawback to aeration systems based on oxygen probes are is the fact that an oxygen probe only determines the oxygen at one location and at one depth. A catfish pond may be ten to twelve acres or more in size, with an average depth of about four feet.
A further drawback is that the oxygen content of the water as measured by an oxygen probe, even if at a level that normally is adequate to avoid stress, may in fact be inadequate to prevent stress, and ultimately death, due to the physical condition of the fish. This situation may result from several common maladies that affect fish such as anemia, nitrite poisoning, parasites on gills, and disease. In other words, fish are sometimes stressed at an oxygen level that is, under normal circumstances, considered quite adequate.
Accordingly, it is an object of the present invention to provide method and apparatus for automatically determining the need for and controlling aeration for aquaculture.
An advantage of the present invention is the provision of method and apparatus for economically controlling oxygen content for aquaculture without being labor-intensive.
A further advantage of the present invention is enhancement of the quality of aquacultural products.